Clean room environments with ceiling grid systems containing high efficiency filters are utilized in many industries. For example, such systems are used when manufacturing components of high tolerance to control airborne contaminants, etc. Typical systems generally employ drop ceilings, above which is a plenum, from which air passes through filter panels in the ceiling grid and into the clean room. Return air plenums can be provided in the floor or sidewalls of the room.
Numerous different grid arrangements have been employed to hold the filter panels. Such filter panels are typically replaceable. Various methods of sealing these filter panels with respect to the supporting framework of grid systems have been used, ranging from soft neoprene mats to the newer non-hardening gel seals.
In many of these prior systems, disadvantages exist. For example, most ceiling grid systems require unobstructed space above the grid in order for a filter panel to be lifted into the grid frame and then lowered into or onto the grid. Typically, these filters are awkward to handle and difficult to install. Further, the risk of mishandling or damaging these filter panels is greatly increased by overhead piping or other obstructions which are often located in the plenum region above the ceiling grid. Moreover, systems which require lifting a filter panel above the grid frame generally require the individuals installing them to be positioned on ladders or steps raised above the clean room floor. Such access requirements increase the risk of injury, as well as the cost and time of properly maintaining these systems.
Frequently, filter panel removal from a ceiling grid requires disassembly of retaining bars or other holding mechanisms. This in itself creates various problems. Disassembly tools or disassembled parts may be easily dropped onto people or equipment beneath. Similarly, these mechanisms may become loose, disassemble and fall due to plenum vibration or oscillation. Also, filter systems having numerous parts may require even greater installation expense, as well as replacement part difficulties.
Other disadvantages of present day clean room ceiling grid filter systems include: gel seals in the grid frame being very messy to handle and install; gaskets on the filters laying on the grid not sealing well; filters being larger than the respective grid openings, making installation and removal difficult; and extra support systems being necessary to hold the ceiling grid because it cannot typically span building joist systems. Easily modified ceiling grids do not usually seal well, whereas, prefabricated grids which seal well cannot be easily modified in the field. Adaptability to small work spaces and low ceiling heights is often impracticle. Many systems provide only one hermetic sealing means.
What has been needed has been an improved, more compact, efficient and effective ceiling grid filter system: providing an easily installed and readily adaptable supporting grid system; providing means for installing filter panels from beneath by pushing the filter panel straight up into the grid from the clean room, so no extra clearance for the filter panels is needed above the grid and associated damage to the filter panel is virtually eliminated; providing means for easily removing and replacing filter panels utilizing a single tool; providing a ceiling grid system which eliminates the messy job of placing gel in the grid; providing a ceiling grid system which incorporates a knife edge and gel seal relationship, thereby permitting a double seal; providing for improved control of filtered air flow thereby eliminating or reducing the size of vortices below grid members and encouraging substantially laminar flow patterns. Also, a ceiling grid filter system which is relatively inexpensive to produce and is easily assembled is preferred.
Objects and advantages of the present invention in achieving these and other goals will become apparent from the following descriptions, taken in connection with the accompanying drawings, wherein are set forth by way of illustration and example certain embodiments of the present invention.